In conventional practice, there have been known navigation devices and navigation systems for searching for a route from a desired departure place to a destination and guiding a user using map data and road data. Practical applications of such navigation devices and navigation systems have included communication-type navigation systems and the like in which a portable phone or a car navigation device installed in an automobile for providing route guidance to a driver is used as a terminal for navigation, a route search request is sent to the route search server, the result is transmitted, and route guidance is received.
Particularly, communication-type navigation systems are used as navigation systems for pedestrians. Other examples of navigation systems for pedestrians include navigation systems which are preferably equipped with a route guidance function that includes a transportation system; and which, in addition to searches and guidance of walking routes, have a function for storing transportation system lines and operating time data for railroads, aircraft, buses, and the like in a route search server, and for providing guidance of routes from desired departure stations to desired destination stations (ridden candidate trains) in addition to searches of and guidance for walking routes. There are also transportation guidance systems which receive and display the distribution of information on lines and time schedules of transportation systems, rideable trains, and the like from an information distribution server without a route search for a walking route.
A route search device and route search method used in a common navigation device and communication navigation system is disclosed in Patent Document 1 (Japanese Laid-open Patent Application No. 2001-165681), for example. This navigation system is configured so as to send information on the departure place and destination from a portable navigation terminal to an information distribution server, and to search for and provide guidance for a route conforming to the search conditions from data on road networks and transportation networks using the information distribution server. The means for moving from the departure place to the destination, e.g., walking, automobile, railroad, aircraft, or other public transportation, or a combination of walking and public transportation are included in the search conditions, and these means are treated as one search condition in a route search.
The information distribution server is provided with map data roads (routes), wherein the nodal points and turning points thereof are nodes, the routes joining nodes together are links, and the cost information (distance and required time) of all the links is the database. The information distribution server can provide a portable navigation terminal with guidance for the shortest possible route by referring to the database, sequentially searching for links extending from the node of the departure place and the node of the destination, and creating a guidance route from the nodes and links having the smallest possible link cost information. Either a method known as the label-correcting method or a method known as the Dijkstra method is used as the method of this manner of route search. In Patent Document 1 hereinbelow, a route search method that uses the Dijkstra method is also disclosed.
A route search system that searches for routes using a transportation system is provided with an operation time database consisting of operation time data of transportation systems incorporated into a database on the basis of a departure date and time, a departure place, a destination, an arrival time, and other route search conditions indicated by a user; and data consisting of a transportation network incorporated into a database on the basis of the operation time database. The configuration is designed so that these databases are referenced, useable transportation means (individual trains and line buses) connecting the departure place to the destination including connections (transfers) are sequentially followed as routes, and one or more candidates of guidance routes (the departure place station, the destination station, lines, trains, and other transportation means) conforming to the route search conditions are suggested. It is common to ensure that the required time, the number of connections, fares, and other conditions can also be designated as route search conditions.
The map data and route search network data provided to a common route guidance system are data on the regions (also known as service target areas) in which the system provides route guidance service. For example, with a normal route guidance system, the regions within a certain country's borders will be the service target, or a specific region within the country's borders will be the service target.
In this case, if the departure place and the destination are within the service target area of the route guidance system, there are no obstacles whatsoever to the route search and the route guidance. However, if the departure place is within the borders of a certain country and the destination is within the borders of another country, it is not possible to search and provide guidance for the total routes from the departure place to the destination. This is because the routes that can be searched and that can have guidance provided by the route guidance system in the departure place are within the range of the country of the departure place, and these routes do not include map data or route search network data of the other country of the destination.
In an on-board navigation device or the like, map data or route search network data of a specified map is stored in the navigation device installed in the vehicle, and when a point outside of the area of the map is designated as the destination, a method is used in which either a route search request is sent to a server having map data or route search network data of the country including the other region, or the map data or route search network data of the needed region is downloaded and a route search is enabled in the navigation device.
For example, an invention of this type of route guidance device is disclosed in the following Patent Document 2 (Japanese Laid-open Patent Application No. 2003-97960). With this route guidance device, when a route search is conducted from a departure place to a destination in a center, a plurality of starting points along the route are marked as candidates. When the starting points are transmitted to the route guidance device, the route guidance device determines which starting points are guide-capable and transmits them to the center. The configuration is designed so that the center performs route searches from the departure place to the starting points, and the guidance device performs route searches from the starting points to the destination, so that the optimum route from the departure place to the destination is provided.
[Patent Document 1]    Japanese Laid-open Patent Application No. 2001-165681 (FIGS. 1 and 2)
[Patent Document 2]    Japanese Laid-open Patent Application No. 2003-97960 (FIGS. 1 and 2)